Communication systems that include antennas can be deployed in a variety of ways. For example, atop cars, trucks, trains, recreational vehicles (RVs), boats, military vehicles such as High Mobility Multipurpose Wheeled Vehicles (HMMWV), commercial aircraft, unmanned aerial vehicles (e.g., Global Hawk), as part of satellites, or networks (e.g., commercial WIMAX, WIFI, or the Army's Warfighter Information Network-Tactical program). Many existing communications systems that operate at C, X, Ku, or Ka-bands use specific types of antennas, for example, reflector (dish) antennas, horn antennas, and/or fixed-beam antennas.
Reflector, horn and other large vertical aperture antennas can require a large bubble radome. When deployed, these antennas typically have a large height. A large height can be problematic where height is limited, such as tunnels, underpasses, under bridges, in parking garages, or driving under branches. In addition, increased height can increase fuel consumption for commercial and military vehicles and aircraft due to added wind resistance. A large height can also increase visibility of the antenna platform, which is problematic for some applications (e.g., military vehicles) where low visibility of the platform is desirable. A large height can also reduce the mission range due to air resistance. In addition to size limitations, reflector and horn antennas typically limit the number of simultaneous beams and links because they typically only radiate in one direction at a time. Narrow-beam antennas such as many reflector antennas can require accurate mechanical steering of the dish, which is slow and greatly reduces the ability to operate on-the-move for off-road vehicles in rough terrain.
Fixed beam antennas can have a lack of beam agility, resulting in loss of link when a platform the antenna is deployed upon rolls or turns. Phased array antennas can be extremely expensive, can have high weight cooling systems, can operate over a limited frequency bandwidth with a limited number of simultaneous beam directions, and can have difficulty forming a beam at very low elevation angles unless they include a large vertical aperture. Existing designs incorporating lenses also have many of the same limitations and problems as phased arrays, or are too large and heavy for practical use.